Customizing the rejection message?

Right now it seems that when SA-Exim rejects a message, it gives the 
mailer a message like this:

   hits=49.0 required=5.0 trigger=40.0

which some mailers will then display to the human being who tried to 
send the message.

Is there any straightforward way to customize this message to something 
like:

   Your message was rejected because it looks like spam.  If it really 
wasn't,
   please re-send it to [email protected].


  ____    |\/|                 Brian Kendig   Set your priorities right.
  \  /\   / ..__.    brian at enchanter net   No one ever said on his
   \/  \__\   _/   http://www.enchanter.net/  death bed, "Gee, if I'd
    \__   __  \_      Be insatiably curious.  only spent more time at
       \____\___\           Ask "why" a lot.  the office."